The accumulation and output of information including pictures and the output of this information to a display or as a hard copy has come to be widely used in recent years.
In the past, techniques for the production of hard copy from soft information have included non-photosensitive recording materials, such as ones using electrical signals, magnetic signals or ink jet systems, and photosensitive materials, for example silver halide photosensitive materials or electrophotographic materials.
In the case of the method using photographic materials, recordings are made using an optical system that emits light in accordance with the image information. This enables not only the optical system itself, image resolution and multi-level recording, but also multi-tone recording to be achieved. Such systems are useful for obtaining high image quality. Because image formation is carried out chemically with the silver halide photographic materials the image quality is higher than systems in which electrophotographic materials are used and greater amounts of information are recorded.
Because image formation with silver halide photographic materials requires wet processing, electrophotographic recording materials are generally favored in fields where the quality requirements are not high.
Recently, progress has been made with photographic image forming systems in which silver halide color photographic materials and compact, simple, rapid development systems are used. Such systems now make it possible to supply photographic prints of very high image quality comparatively easily and cheaply. Using such a system is used to obtain images from soft information permits high image quality hard copy to be supplied easily and cheaply.
Special means are required to carry out the rapid and simple development processing of such silver halide color photographic materials. The silver halide color photographic material must combine adequate performance of its photosensitive wavelengths, optimum speed and color separation for matching the optical system which is being used and the application, and it must also have a photographic speed which is adequately stable.
In the past, color copying techniques include copying machines and laser printers using electrophotographic techniques, and a combination of LED, silver halide based heat development and dye diffusion systems. Silver halide color photographic materials comprising a support having established thereon at least three silver halide emulsion layers in which conventional color couplers are used and in which at least two layers are spectrally sensitized with dyes to laser light in the infrared region are disclosed in JP-A-61-137149. (The term "JP-A" as used herein signifies an "unexamined published Japanese patent application".)
JP-A-63-197947 describes full color recording materials of at least three photosensitive layers containing color couplers. At least one of these layers is photosensitive to LED or semiconductor laser light, and is spectrally sensitized so that the spectrally sensitized peak wavelength is longer that about 670 nm. Colored images are obtained by means of a scanning exposure with subsequent development processing. The method describes spectral sensitization which is stable and provides high speed, and provides a method of using dyes.
A color photographic material image recording system wherein yellow, magenta, and cyan color formation is controlled with three light beams of different wavelengths, for example green, red and infrared light beams, respectively, is disclosed in JP-A-55-13505.
A continuous tone scanning type printer which has a semiconductor laser output controlling mechanism is described by S. H. Baek on pages 245-247 of the published papers of the Fourth International Symposium on Non-impact Printing (SPSE).
A method of using silver halide color photographic materials to produce hard copy from soft information generally provides high image quality in a stable manner more readily than a non-photosensitive recording method or a method in which electrophotographic materials are used. If semiconductor lasers are used for a scanning exposure system then, an exposing apparatus can be made that is compact and inexpensive.
However, the wavelength of usable semiconductor lasers cannot, at the present time, be selected arbitrarily. Most recently, lasers of wavelength in the vicinity of 670 nm have become available. Many practical lasers already exist that produce light in the infrared wavelengths.
At least three photosensitive layers that are spectrally sensitized to different photosensitive wavelength regions are required in a subtractive color photographic system such as the present invention. At least one or two of these layers and, depending on the particular case, three or more of these layers must be photosensitive to the infrared wavelength region.
The drawback of semiconductor lasers is that output of elements in the shorter wavelength region of the visible region or infrared region close to the visible region is not very large and it is difficult to obtain stable output.
Thus, the characteristics required of a photosensitive material for use with semiconductor lasers of this type are high photographic speed, stable performance regardless of fluctuations of the wavelength and other characteristics of the semiconductor laser and the realization of these features within the light wavelength range of the infrared region. It is difficult to satisfy these requirements in the infrared region using just silver iodobromides which are generally useful for obtaining high photographic speeds.
On the other hand, if a color image is to be obtained from an exposed photographic material using a system of this type then silver iodobromide has an adverse effect on the rapidity of the process and it is well known that silver chlorobromide is preferred. It is also well known in these circumstances, in particular, that so-called high silver chloride emulsions which contain a high proportion of silver chloride are preferred.
However, it is difficult to satisfy the aforementioned requirements in the infrared region with such a high silver chloride emulsion. That is to say, silver chloride emulsions are not advantageous for spectral sensitization with infrared spectrally sensitizing dyes. This makes it difficult to achieve high photographic speed and stable photographic speed with respect to various exposure conditions using silver chloride emulsions.